The influence of doping and annealing onto the lattice dynamics, band structure and free charge carrier properties in monoclinic gallium aluminum oxide semiconductor alloys

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Non-technical Description: This project provides a scientific basis for development of novel semiconductor material for electronic devices that could enable real-time low-loss electric power distribution capability within the electric grid. Such distribution can be controlled by high-power electronic devices capable of switching and distributing high voltages and loads. As a new class of semiconductor materials, gallium aluminum oxide emerges as a promising candidate for fabrication of such devices. This project investigates the influence of doping and composition onto the resulting electronic properties of the material by employing a variety of theoretical and experimental characterization techniques. This project offers various training opportunities for undergraduate and graduate students, along with various outreach activities targeting K-12 students, teachers, minorities and underrepresented groups. The project includes Nebraska high-school and middle-school student summer research programs and after-school science education activities, and annual public Social and academic outreach programs are expanded to include demonstrations and Sunday presentations at the University of Nebraska State Museum on power electronics and the electric grid of the future for elementary to high school students.Technical Description: The project focuses on a fundamental material investigation of novel wide-bandgap material with potential in high power electronic applications. The research investigates the effect of doping and annealing on the electronic properties of semiconductor aluminum gallium oxide alloys with monoclinic symmetry. The main objectives are to determine the phonon, band structure and free charge carrier effective mass and mobility parameters, including their anisotropy, as a function of: (i) aluminum composition variation, (ii) tin, germanium and silicon doping concentrations and (iii) annealing under different gaseous environments in wide temperature ranges. The project combines computational theory and experimental characterization. Density functional theory calculations are performed to predict the effects of doping (defects) and alloying and to guide the applications of the experimental techniques - generalized spectroscopic ellipsometry and the optical Hall effect - to determine the electronic, phonon and transport properties in single crystals and heterostructures of low-symmetry semiconductors. Additional techniques include Raman spectroscopy and in-situ high-temperature studies. This research contributes to the technological development of high power electronic devices based on novel monoclinic semiconductor materials and provides education and research training possibilities for graduate students and young researchers in advanced semiconductor technology in culturally diverse environment.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.